This invention relates to aqueous automatic dishwashing detergent compositions which have a yield value and are shear-thinning. Compositions of this general type are known. Examples of such compositions are disclosed in U.S. Pat. No. 4,116,851 to Rupe et al, issued September 26, 1978; U.S. Pat. No. 4,431,559 to Ulrich, issued Feb. 14, 1984; U.S. Pat. No. 4,511,487 to Pruhs et al, issued April 16, 1985; U.S. Pat. No. 4,512,908 to Heile, issued April 23, 1985; Canadian Patent 1,031,229, Bush et al; European Patent Application 0130678, Heile, published Jan. 9, 1985; European Patent Application 0176163, Robinson, published April 2, 1986; UK Patent Application 2,116,199A, Julemont et al, published Sept. 21, 1983; UK Patent Application 2,140,450A, Julemont et al, published Nov. 29, 1984; UK Patent Application 2,163,447A, Colarusso, published Feb. 26, 1986; and UK Patent Application 2,164,350A, Lai et al, published March 19, 1986.
U.K. Patent Application 2,176,495A, to Drapler et al, published December 31, 1986, discloses incorporation of 0.1 to 0.2 wt. percent of a polyvalent metal salt of a long chain fatty acid in a gel-like automatic dishwasher detergent composition to improve stability of the composition. Aluminum tristearate is taught to be the preferred salt.
U.K. Patent Application 2,185,037A, Dixit (Colgate), published July 8, 1987, discloses that aqueous cleaning compositions containing inorganic builder salts and other functional inorganic salts, chlorine bleach, and bleach-stable surfactant are transformed into thixotropic liquid automatic dishwasher detergent compositions by incorporation of 0.03 to 0.5 wt. percent of stearic acid.
It has now been found that incorporation of metal salts of long chain hydroxy fatty acids into automatic dishwashing detergent compositions inhibits tarnishing of sterling and silver-plated flatware in products containing bleach and caustic.
The state of the art liquid automatic dishwashing detergent compositions typically thickened with clay still suffer from phase separation upon storage under certain conditions. However, it has now been discovered that such compositions are improved by the utilization of certain thickening and stabilizing agents. More specifically, automatic dishwashing detergent compositions comprising a polycarboxylate thickener and certain phosphate ester stabilizers have improved phase stability and cohesiveness.
The use of polyacrylic thickeners in liquid automatic dishwashing detergent compositions is known. See, for example, U.K. Patent Application 2,185,037, Dixit, published July 8, 1987, which discloses liquid automatic dishwashing detergents which contain a long chain carboxylic or polycarboxylic acid as the thickener. Also, European Patent Application 0239379, Brumbaugh, published September 9, 1987, teaches that polyacrylate is useful for water spot reduction in liquid automatic dishwashing detergent compositions. U.S. Pat. No. 4,226,736 to Bush et al, issued October 7, 1980, teaches that a polymer of acrylic acid can be used as a thickener in liquid automatic dishwashing detergents instead of clay.
The use of phosphate esters, in general, in automatic dishwashing detergent compositions is also known. See, for example, U.K. Patent Application 2,116,199, Julemont et al, published September 21, 1983, which teaches the use of an alkyl ester of phosphoric acid as a foam depressor.
The combination of polyacrylate thickeners and phosphate ester plus clay has also been taught in U.K. Patent Application 1,164,350, Lai et al, published March 19, 1986. The polyacrylate thickeners taught to be useful have molecular weights of up to 500,000 (preferably up to 50,000). These compositions are said to be useful for protection of glazing on fine china.
Enhanced phase stability and improved dispensing of the product from its container are achieved if a polyacrylate thickener and phosphate ester component are used together in the absence of clay in the automatic dishwashing detergent compositions disclosed herein.